Measures to be taken if readout does not match specification
- Select display group "001" in "Read measuring value block" function Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
- Repeat cooling performance test --> «A/C cooling output, checking»(ref-289225-S08271818162008062700000) .
| Observe display field "1" and "4" during cooling performance test. Was activation of A/C Compressor Regulator Valve N280 switched off during cooling performance test (control current dropped below 0.50 A)? | |||
|---|---|---|---|
| ↓ yes ↓ | ↓ no ↓ | ||
| Interrogate fault memory, eliminate faults displayed and erase fault memory. Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function. | Did the pressure in refrigerant circuit (display field "4") increase during cooling performance test? | ||
| Read measuring value block, display group "002" (compressor switch-off requirements) and eliminate cause for switch-off Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function. | ↓ yes ↓ | ↓ no ↓ | |
| Repeat cooling output test. | ↓ Continuation: Increase in pressure in refrigerant circuit ↓ | Transfer vehicle to an A/C system service point workshop (malfunction in refrigerant circuit). | |
Increase in pressure in refrigerant circuit
- Open hood.
- Repeat cooling performance test --> «A/C cooling output, checking»(ref-289225-S08271818162008062700000) .
| Do Coolant Fans V7 run during cooling performance test (speed depends on coolant temperature and pressure in refrigerant circuit, speed is determined by Engine Control Module (ECM))? Depending on version of Climatronic Control Module J255 , Coolant Fans V7 are only activated from certain pressure in refrigerant circuit. | |||
|---|---|---|---|
| ↓ yes ↓ | ↓ no ↓ | ||
| Read measuring value block, display group "001" (pressure in refrigerant circuit) and "022" (activation of coolant fans) Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function. Does Coolant Fan V7 run at increased speed when pressure in refrigerant circuit increases? | Check activation of Coolant Fan V7 , e.g. in function "output Diagnostic Test Mode (DTM)". Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function. Repair activation of Coolant Fan V7. Repeat cooling performance test --> A/C cooling output, checking . | ||
| ↓ yes ↓ | ↓ no ↓ | ||
| Transfer vehicle to an A/C system service point workshop (malfunction in refrigerant circuit). | Check activation of Coolant Fan V7 , e.g. in function "output Diagnostic Test Mode (DTM)". Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function. Repair activation of Coolant Fan V7. | ||
Note. Pressure in refrigerant circuit is governed by various factors of influence. However, at an ambient temperature between 20 to 25°C the pressure should not exceed more than 20 bar. Due to high coolant performance, pressures up to 31 bar may occur under extreme operating conditions (e.g. in southern countries with high ambient temperatures, "stop and go" traffic and high humidity). At ambient temperatures below 25°C, pressure in refrigerant circuit does not normally exceed 16 bar (radiator fan runs and cools condenser). Climatronic Control Module J255 calculates pressure in refrigerant circuit via the duty cycle (read measuring value block, display group "001" , display field "3"). At a duty cycle less than 12.5% (corresponds to approx. 1.8 bar absolute pressure) and greater than 87.5% (corresponds to approx. 32 bar absolute pressure), does not switch on compressor (A/C Compressor Regulator Valve N280 is not activated). Compressor is only switched on again after duty cycle has become greater than 12.5% (corresponds to 1.8 bar absolute pressure) or less than 48% (corresponds to 16 bar absolute pressure). To prevent abrupt compressor shut-off in case of excessive pressure in refrigerant circuit or excessive coolant temperature, regulates compressor performance: - As soon as pressure in refrigerant circuit exceeds 30 bar (absolute pressure), full compressor performance is only enabled again after pressure has become less than 27 bar. - As soon as coolant temperature exceeds 115°C (full shutdown at 118°C). If pressure in refrigerant circuit was greater than 32 bar (duty cycle greater than 87.5%), compressor is only switched on again by if pressure drops below 29 bar (duty cycle less than 84%). Further notes on pressure in refrigerant circuit can be found in --> Read Measuring Value Block ("Read measuring value block" , display group "001") and Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" function.
Tightening torques
| Component | Nm |
|---|---|
| A/C compressor to bracket | 25 |
| Refrigerant lines to A/C compressor | > Refrigerant lines, disconnecting and connecting at compressor |
Compressor drive shaft, loosening and tightening
Note. Extensive preliminary work is needed in order to be able to loosen the compressor drive shaft --> Compressor, removing and installing - vehicles with 10-cyl. engine (Audi S8) (Compressor, removing and installing on vehicles with 10-cyl. engine) or --> A/C compressor, removing and installing - vehicles with 8-cyl. FSI engine (Compressor, removing and installing on vehicles with 8-cyl. FSI engine) Drive shaft can also be checked and tightened without opening the refrigerant circuit.
Compressor drive shaft, tightening
- Hold compressor drive shaft - A - in place using an open-end wrench and turn compressor drive unit - B - in direction of arrow - D - (tightening torque 60 Nm).
- After tightening compressor drive shaft, check installation position of boot - E
Capacities
Refrigerant R134a and refrigerant oil capacities: --> 87 - AIR CONDITIONING
- Evacuating and charging refrigerant circuit --> «87 - AIR CONDITIONING»(ref-289226-S15694198272008062700000)
Note. Depending on compressor type ("6 SEU 14" , "7 SEU 16" or "7 SEU 17") different refrigerant oil fill capacities are designated for the refrigerant circuit and --> 87 - AIR CONDITIONING Compressor as replacement part has different oil fill capacities, therefore note the exact part number and --> 87 - AIR CONDITIONING . The reason for the different oil capacities in the compressor lies in the design of the compressor itself, note these oil capacities. Too much oil in the circuit leads to higher pressures and reduces cooling performance of the system. Too little oil may lead to lubrication problems in the compressor. When charging the A/C system, always use maximum amount of refrigerant R134a, as some of the refrigerant remains in the hose of the refrigerant recovery, recycling and recharging unit. Refrigerant circuit may only be filled with approved refrigerant oils. Zexel, Sanden and Denso compressors require different refrigerant oils: --> 87 - AIR CONDITIONING At this time, refrigerant oil G 052 300 A2 is to be used for Denso compressors --> 87 - AIR CONDITIONING . Use only the specified oil from a sealed container and always reseal oil container immediately after use (PAG oil absorbs moisture). Do not use oil if it is contaminated with moisture or if oil container has been left open. Additional 87 - AIR CONDITIONING